1
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Holstein TW. Hunger and satiety: Neuronal dynamics in Hydra behavior. Cell Rep 2024; 43:114264. [PMID: 38787721 DOI: 10.1016/j.celrep.2024.114264] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2024] [Revised: 05/04/2024] [Accepted: 05/07/2024] [Indexed: 05/26/2024] Open
Abstract
Hormonal and neuronal inputs to the brain control how much animals eat. The origins of this behavior were unclear, but in this issue of Cell Reports, Giez et al.1 describe specific neurons inhibiting feeding in evolutionary ancient animals without brain.
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Affiliation(s)
- Thomas W Holstein
- Centre for Organismal Studies, Heidelberg University, INF 230 Heidelberg, Germany.
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2
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Keramidioti A, Schneid S, Busse C, Cramer von Laue C, Bertulat B, Salvenmoser W, Hess M, Alexandrova O, Glauber KM, Steele RE, Hobmayer B, Holstein TW, David CN. A new look at the architecture and dynamics of the Hydra nerve net. eLife 2024; 12:RP87330. [PMID: 38407174 PMCID: PMC10942621 DOI: 10.7554/elife.87330] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/27/2024] Open
Abstract
The Hydra nervous system is the paradigm of a 'simple nerve net'. Nerve cells in Hydra, as in many cnidarian polyps, are organized in a nerve net extending throughout the body column. This nerve net is required for control of spontaneous behavior: elimination of nerve cells leads to polyps that do not move and are incapable of capturing and ingesting prey (Campbell, 1976). We have re-examined the structure of the Hydra nerve net by immunostaining fixed polyps with a novel antibody that stains all nerve cells in Hydra. Confocal imaging shows that there are two distinct nerve nets, one in the ectoderm and one in the endoderm, with the unexpected absence of nerve cells in the endoderm of the tentacles. The nerve nets in the ectoderm and endoderm do not contact each other. High-resolution TEM (transmission electron microscopy) and serial block face SEM (scanning electron microscopy) show that the nerve nets consist of bundles of parallel overlapping neurites. Results from transgenic lines show that neurite bundles include different neural circuits and hence that neurites in bundles require circuit-specific recognition. Nerve cell-specific innexins indicate that gap junctions can provide this specificity. The occurrence of bundles of neurites supports a model for continuous growth and differentiation of the nerve net by lateral addition of new nerve cells to the existing net. This model was confirmed by tracking newly differentiated nerve cells.
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Affiliation(s)
- Athina Keramidioti
- Department of Biology, Ludwig-Maximilians-University MunichMartinsriedGermany
| | - Sandra Schneid
- Department of Biology, Ludwig-Maximilians-University MunichMartinsriedGermany
| | - Christina Busse
- Department of Biology, Ludwig-Maximilians-University MunichMartinsriedGermany
| | | | - Bianca Bertulat
- Centre for Organismal Studies (COS) Heidelberg, Heidelberg UniversityHeidelbergGermany
| | - Willi Salvenmoser
- Department of Zoology and Center for Molecular Biosciences Innsbruck (CMBI), University of InnsbruckInnsbruckAustria
| | - Martin Hess
- Department of Biology, Ludwig-Maximilians-University MunichMartinsriedGermany
| | - Olga Alexandrova
- Department of Biology, Ludwig-Maximilians-University MunichMartinsriedGermany
| | - Kristine M Glauber
- Department of Biological Chemistry, University of CaliforniaIrvineUnited States
| | - Robert E Steele
- Department of Biological Chemistry, University of CaliforniaIrvineUnited States
| | - Bert Hobmayer
- Department of Zoology and Center for Molecular Biosciences Innsbruck (CMBI), University of InnsbruckInnsbruckAustria
| | - Thomas W Holstein
- Centre for Organismal Studies (COS) Heidelberg, Heidelberg UniversityHeidelbergGermany
| | - Charles N David
- Department of Biology, Ludwig-Maximilians-University MunichMartinsriedGermany
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3
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Holstein TW. Evolution: Neuronal control of an archaic mouth. Curr Biol 2023; 33:R1304-R1306. [PMID: 38113845 DOI: 10.1016/j.cub.2023.11.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2023]
Abstract
Cnidarians (corals, hydras, jellyfish, sea anemones) are prey-devouring creatures with a simple nervous system, the function of which is largely unknown. A new study on the freshwater polyp Hydra has now uncovered the neuronal circuits that control its feeding behavior.
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Affiliation(s)
- Thomas W Holstein
- Centre for Organismal Studies (COS), Department of Molecular Evolution and Genomics, Heidelberg University, Im Neuenheimer Feld 230, D-69120 Heidelberg, Germany.
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4
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Holstein TW. The Hydra stem cell system - Revisited. Cells Dev 2023; 174:203846. [PMID: 37121433 DOI: 10.1016/j.cdev.2023.203846] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Revised: 04/12/2023] [Accepted: 04/25/2023] [Indexed: 05/02/2023]
Abstract
Cnidarians are >600 million years old and are considered the sister group of Bilateria based on numerous molecular phylogenetic studies. Apart from Hydra, the genomes of all major clades of Cnidaria have been uncovered (e.g. Aurelia, Clytia, Nematostella and Acropora) and they reveal a remarkable completeness of the metazoan genomic toolbox. Of particular interest is Hydra, a model system of aging research, regenerative biology, and stem cell biology. With the knowledge gained from scRNA research, it is now possible to characterize the expression profiles of all cell types with great precision. In functional studies, our picture of the Hydra stem cell biology has changed, and we are in the process of obtaining a clear picture of the homeostasis and properties of the different stem cell populations. Even though Hydra is often compared to plant systems, the new data on germline and regeneration, but also on the dynamics and plasticity of the nervous system, show that Hydra with its simple body plan represents in a nutshell the prototype of an animal with stem cell lineages, whose properties correspond in many ways to Bilateria. This review provides an overview of the four stem cell lineages, the two epithelial lineages that constitute the ectoderm and the endoderm, as well as the multipotent somatic interstitial lineage (MPSC) and the germline stem cell lineage (GSC), also known as the interstitial cells of Hydra.
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Affiliation(s)
- Thomas W Holstein
- Heidelberg University, Centre for Organismal Studies (COS), Molecular Evolution and Genomics, Im Neuenheimer Feld 230, D-69120 Heidelberg, Germany.
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5
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Primack AS, Cazet JF, Little HM, Mühlbauer S, Cox BD, David CN, Farrell JA, Juliano CE. Differentiation trajectories of the Hydra nervous system reveal transcriptional regulators of neuronal fate. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.15.531610. [PMID: 36993575 PMCID: PMC10055148 DOI: 10.1101/2023.03.15.531610] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 04/27/2023]
Abstract
The small freshwater cnidarian polyp Hydra vulgaris uses adult stem cells (interstitial stem cells) to continually replace neurons throughout its life. This feature, combined with the ability to image the entire nervous system (Badhiwala et al., 2021; Dupre & Yuste, 2017) and availability of gene knockdown techniques (Juliano, Reich, et al., 2014; Lohmann et al., 1999; Vogg et al., 2022), makes Hydra a tractable model for studying nervous system development and regeneration at the whole-organism level. In this study, we use single-cell RNA sequencing and trajectory inference to provide a comprehensive molecular description of the adult nervous system. This includes the most detailed transcriptional characterization of the adult Hydra nervous system to date. We identified eleven unique neuron subtypes together with the transcriptional changes that occur as the interstitial stem cells differentiate into each subtype. Towards the goal of building gene regulatory networks to describe Hydra neuron differentiation, we identified 48 transcription factors expressed specifically in the Hydra nervous system, including many that are conserved regulators of neurogenesis in bilaterians. We also performed ATAC-seq on sorted neurons to uncover previously unidentified putative regulatory regions near neuron-specific genes. Finally, we provide evidence to support the existence of transdifferentiation between mature neuron subtypes and we identify previously unknown transition states in these pathways. All together, we provide a comprehensive transcriptional description of an entire adult nervous system, including differentiation and transdifferentiation pathways, which provides a significant advance towards understanding mechanisms that underlie nervous system regeneration.
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Affiliation(s)
- Abby S Primack
- Department of Molecular and Cellular Biology, University of California, Davis, CA 95616
| | - Jack F Cazet
- Department of Molecular and Cellular Biology, University of California, Davis, CA 95616
| | - Hannah Morris Little
- Department of Molecular and Cellular Biology, University of California, Davis, CA 95616
| | - Susanne Mühlbauer
- Department of Plant Biochemistry, Ludwig-Maximilians-University Munich, 82152 Planegg-Martinsried, Germany
| | - Ben D Cox
- Department of Molecular and Cellular Biology, University of California, Davis, CA 95616
| | - Charles N David
- Department of Biology, Ludwig-Maximilians-University Munich, 82152 Martinsried, Germany
| | - Jeffrey A Farrell
- Division of Developmental Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD 20814, USA
| | - Celina E Juliano
- Department of Molecular and Cellular Biology, University of California, Davis, CA 95616
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6
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A chromosome-scale epigenetic map of the Hydra genome reveals conserved regulators of cell state. Genome Res 2023; 33:283-298. [PMID: 36639202 PMCID: PMC10069465 DOI: 10.1101/gr.277040.122] [Citation(s) in RCA: 14] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Accepted: 01/10/2023] [Indexed: 01/15/2023]
Abstract
The epithelial and interstitial stem cells of the freshwater polyp Hydra are the best-characterized stem cell systems in any cnidarian, providing valuable insight into cell type evolution and the origin of stemness in animals. However, little is known about the transcriptional regulatory mechanisms that determine how these stem cells are maintained and how they give rise to their diverse differentiated progeny. To address such questions, a thorough understanding of transcriptional regulation in Hydra is needed. To this end, we generated extensive new resources for characterizing transcriptional regulation in Hydra, including new genome assemblies for Hydra oligactis and the AEP strain of Hydra vulgaris, an updated whole-animal single-cell RNA-seq atlas, and genome-wide maps of chromatin interactions, chromatin accessibility, sequence conservation, and histone modifications. These data revealed the existence of large kilobase-scale chromatin interaction domains in the Hydra genome that contain transcriptionally coregulated genes. We also uncovered the transcriptomic profiles of two previously molecularly uncharacterized cell types: isorhiza-type nematocytes and somatic gonad ectoderm. Finally, we identified novel candidate regulators of cell type-specific transcription, several of which have likely been conserved at least since the divergence of Hydra and the jellyfish Clytia hemisphaerica more than 400 million years ago.
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7
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Abstract
Neurons are the fundamental building blocks of nervous systems. It appears intuitive that the human brain is made up of hundreds, if not thousands different types of neurons. Conversely, the seemingly diffuse nerve net of Cnidaria is often assumed to be simple. However, evidence that the Cnidaria nervous system is indeed simple is sparse. Recent technical advances make it possible to assess the diversity and function of neurons with unprecedented resolution. Transgenic animals expressing genetically encoded Calcium sensors allow direct physiological assessments of neural responses within the nerve net and provide insight into the spatial organization of the nervous system. Moreover, response and activity patterns allow the characterization of cell types on a functional level. Molecular and genetic identities on the other hand can be assessed combining single-cell transcriptomic analysis with correlations of gene expression in defined neurons. Here I review recent advances on these two experimental strategies focusing on Hydra, Nematostella, and Clytia.
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Affiliation(s)
- Simon G Sprecher
- Department of Biology, University of Fribourg, Fribourg, Switzerland
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8
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Traffic light Hydra allows for simultaneous in vivo imaging of all three cell lineages. Dev Biol 2022; 488:74-80. [DOI: 10.1016/j.ydbio.2022.05.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2021] [Revised: 05/06/2022] [Accepted: 05/10/2022] [Indexed: 11/19/2022]
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9
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Farooq M, Khan AW, Kim MS, Choi S. The Role of Fibroblast Growth Factor (FGF) Signaling in Tissue Repair and Regeneration. Cells 2021; 10:cells10113242. [PMID: 34831463 PMCID: PMC8622657 DOI: 10.3390/cells10113242] [Citation(s) in RCA: 48] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2021] [Revised: 11/10/2021] [Accepted: 11/16/2021] [Indexed: 02/06/2023] Open
Abstract
Fibroblast growth factors (FGFs) are a large family of secretory molecules that act through tyrosine kinase receptors known as FGF receptors. They play crucial roles in a wide variety of cellular functions, including cell proliferation, survival, metabolism, morphogenesis, and differentiation, as well as in tissue repair and regeneration. The signaling pathways regulated by FGFs include RAS/mitogen-activated protein kinase (MAPK), phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K)–protein kinase B (AKT), phospholipase C gamma (PLCγ), and signal transducer and activator of transcription (STAT). To date, 22 FGFs have been discovered, involved in different functions in the body. Several FGFs directly or indirectly interfere with repair during tissue regeneration, in addition to their critical functions in the maintenance of pluripotency and dedifferentiation of stem cells. In this review, we summarize the roles of FGFs in diverse cellular processes and shed light on the importance of FGF signaling in mechanisms of tissue repair and regeneration.
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Affiliation(s)
- Mariya Farooq
- Department of Molecular Science and Technology, Ajou University, Suwon 16499, Korea; (M.F.); (A.W.K.); (M.S.K.)
| | - Abdul Waheed Khan
- Department of Molecular Science and Technology, Ajou University, Suwon 16499, Korea; (M.F.); (A.W.K.); (M.S.K.)
| | - Moon Suk Kim
- Department of Molecular Science and Technology, Ajou University, Suwon 16499, Korea; (M.F.); (A.W.K.); (M.S.K.)
| | - Sangdun Choi
- Department of Molecular Science and Technology, Ajou University, Suwon 16499, Korea; (M.F.); (A.W.K.); (M.S.K.)
- S&K Therapeutics, Ajou University Campus Plaza 418, 199 Worldcup-ro, Yeongtong-gu, Suwon 16502, Korea
- Correspondence:
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10
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Badhiwala KN, Primack AS, Juliano CE, Robinson JT. Multiple neuronal networks coordinate Hydra mechanosensory behavior. eLife 2021; 10:e64108. [PMID: 34328079 PMCID: PMC8324302 DOI: 10.7554/elife.64108] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Accepted: 06/17/2021] [Indexed: 12/11/2022] Open
Abstract
Hydra vulgaris is an emerging model organism for neuroscience due to its small size, transparency, genetic tractability, and regenerative nervous system; however, fundamental properties of its sensorimotor behaviors remain unknown. Here, we use microfluidic devices combined with fluorescent calcium imaging and surgical resectioning to study how the diffuse nervous system coordinates Hydra's mechanosensory response. Mechanical stimuli cause animals to contract, and we find this response relies on at least two distinct networks of neurons in the oral and aboral regions of the animal. Different activity patterns arise in these networks depending on whether the animal is contracting spontaneously or contracting in response to mechanical stimulation. Together, these findings improve our understanding of how Hydra's diffuse nervous system coordinates sensorimotor behaviors. These insights help reveal how sensory information is processed in an animal with a diffuse, radially symmetric neural architecture unlike the dense, bilaterally symmetric nervous systems found in most model organisms.
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Affiliation(s)
| | - Abby S Primack
- Department of Molecular and Cellular BiologyUniversity of California, DavisUnited States
| | - Celina E Juliano
- Department of Molecular and Cellular BiologyUniversity of California, DavisUnited States
| | - Jacob T Robinson
- Department of Bioengineering, Rice UniversityHoustonUnited States
- Department of Electrical and Computer Engineering, Rice UniversityHoustonUnited States
- Department of Neuroscience, Baylor College of MedicineHoustonUnited States
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11
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Tzouanas CN, Kim S, Badhiwala KN, Avants BW, Robinson JT. Hydra vulgaris shows stable responses to thermal stimulation despite large changes in the number of neurons. iScience 2021; 24:102490. [PMID: 34095784 PMCID: PMC8164038 DOI: 10.1016/j.isci.2021.102490] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Revised: 02/03/2021] [Accepted: 04/27/2021] [Indexed: 11/27/2022] Open
Abstract
Many animals that lose neural tissue to injury or disease can maintain behavioral repertoires by regenerating new neurons or reorganizing existing neural circuits. However, most neuroscience small model organisms lack this high degree of neural plasticity. We show that Hydra vulgaris can maintain stable sensory-motor behaviors despite 2-fold changes in neuron count, due to naturally occurring size variation or surgical resection. Specifically, we find that both behavioral and neural responses to rapid temperature changes are maintained following these perturbations. We further describe possible mechanisms for the observed neural activity and argue that Hydra's radial symmetry may allow it to maintain stable behaviors when changes in the numbers of neurons do not selectively eliminate any specific neuronal cell type. These results suggest that Hydra provides a powerful model for studying how animals maintain stable sensory-motor responses within dynamic neural circuits and may lead to the development of general principles for injury-tolerant neural architectures.
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Affiliation(s)
| | - Soonyoung Kim
- Department of Electrical and Computer Engineering, Rice University, 6100 Main Street, Houston, TX 77005, USA
| | - Krishna N. Badhiwala
- Department of Bioengineering, Rice University, 6100 Main Street, Houston, TX 77005, USA
| | - Benjamin W. Avants
- Department of Electrical and Computer Engineering, Rice University, 6100 Main Street, Houston, TX 77005, USA
| | - Jacob T. Robinson
- Department of Bioengineering, Rice University, 6100 Main Street, Houston, TX 77005, USA
- Department of Electrical and Computer Engineering, Rice University, 6100 Main Street, Houston, TX 77005, USA
- Department of Neuroscience, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
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12
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Noro Y, Shimizu H, Mineta K, Gojobori T. A single neuron subset governs a single coactive neuron circuit in Hydra vulgaris, representing a possible ancestral feature of neural evolution. Sci Rep 2021; 11:10828. [PMID: 34031445 PMCID: PMC8144215 DOI: 10.1038/s41598-021-89325-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2020] [Accepted: 04/23/2021] [Indexed: 12/03/2022] Open
Abstract
The last common ancestor of Bilateria and Cnidaria is believed to be one of the first animals to develop a nervous system over 500 million years ago. Many of the genes involved in the neural function of the advanced nervous system in Bilateria are well conserved in Cnidaria. Thus, the cnidarian Hydra vulgaris is a good model organism for the study of the putative primitive nervous system in its last common ancestor. The diffuse nervous system of Hydra consists of several peptidergic neuron subsets. However, the specific functions of these subsets remain unclear. Using calcium imaging, here we show that the neuron subsets that express neuropeptide, Hym-176, function as motor circuits to evoke longitudinal contraction. We found that all neurons in a subset defined by the Hym-176 gene (Hym-176A) or its paralogs (Hym-176B) expression are excited simultaneously, followed by longitudinal contraction. This indicates not only that these neuron subsets have a motor function but also that a single molecularly defined neuron subset forms a single coactive circuit. This is in contrast with the bilaterian nervous system, where a single molecularly defined neuron subset harbors multiple coactive circuits, showing a mixture of neurons firing with different timings. Furthermore, we found that the two motor circuits, one expressing Hym-176B in the body column and the other expressing Hym-176A in the foot, are coordinately regulated to exert region-specific contraction. Our results demonstrate that one neuron subset is likely to form a monofunctional circuit as a minimum functional unit to build a more complex behavior in Hydra. This simple feature (one subset, one circuit, one function) found in Hydra may represent the simple ancestral condition of neural evolution.
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Affiliation(s)
- Yukihiko Noro
- Computational Biosciences Research Center, King Abdullah University of Science and Technology, Thuwal, 23955-6900, Kingdom of Saudi Arabia
| | - Hiroshi Shimizu
- Computational Biosciences Research Center, King Abdullah University of Science and Technology, Thuwal, 23955-6900, Kingdom of Saudi Arabia
| | - Katsuhiko Mineta
- Computational Biosciences Research Center, King Abdullah University of Science and Technology, Thuwal, 23955-6900, Kingdom of Saudi Arabia
| | - Takashi Gojobori
- Computational Biosciences Research Center, King Abdullah University of Science and Technology, Thuwal, 23955-6900, Kingdom of Saudi Arabia.
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13
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Takahashi T. Comparative Aspects of Structure and Function of Cnidarian Neuropeptides. Front Endocrinol (Lausanne) 2020; 11:339. [PMID: 32528418 PMCID: PMC7266959 DOI: 10.3389/fendo.2020.00339] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Accepted: 04/30/2020] [Indexed: 12/18/2022] Open
Abstract
Cnidarians are early-branching animals in the eukaryotic tree of life. The phylum Cnidaria are divided into five classes: Scyphozoa (true jellyfish), Cubozoa (box jellyfish), Hydrozoa (species, Hydra and Hydractinia), Anthozoa (sea anemone, corals, and sea pen), and Staurozoa (stalked jellyfish). Peptides play important roles as signaling molecules in development and differentiation in cnidaria. For example, cnidaria use peptides for cell-to cell communication. Recent discoveries show that Hydra neuropeptides control several biological processes including muscle contraction, neuron differentiation, and metamorphosis. Here, I describe the structure and functions of neuropeptides in Hydra and other cnidarian species. I also discuss that so-called primitive nervous system of Hydra is in more complex than generally believed. I also discuss how cnidaria use peptides for communication among cells rather than in higher animals.
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14
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Goel T, Wang R, Martin S, Lanphear E, Collins EMS. Linalool acts as a fast and reversible anesthetic in Hydra. PLoS One 2019; 14:e0224221. [PMID: 31648269 PMCID: PMC6812832 DOI: 10.1371/journal.pone.0224221] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Accepted: 10/08/2019] [Indexed: 01/23/2023] Open
Abstract
The ability to make transgenic Hydra lines has allowed for quantitative in vivo studies of Hydra regeneration and physiology. These studies commonly include excision, grafting and transplantation experiments along with high-resolution imaging of live animals, which can be challenging due to the animal’s response to touch and light stimuli. While various anesthetics have been used in Hydra studies, they tend to be toxic over the course of a few hours or their long-term effects on animal health are unknown. Here, we show that the monoterpenoid alcohol linalool is a useful anesthetic for Hydra. Linalool is easy to use, non-toxic, fast acting, and reversible. It has no detectable long-term effects on cell viability or cell proliferation. We demonstrate that the same animal can be immobilized in linalool multiple times at intervals of several hours for repeated imaging over 2–3 days. This uniquely allows for in vivo imaging of dynamic processes such as head regeneration. We directly compare linalool to currently used anesthetics and show its superior performance. Linalool will be a useful tool for tissue manipulation and imaging in Hydra research in both research and teaching contexts.
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Affiliation(s)
- Tapan Goel
- Department of Physics, University of California San Diego, La Jolla, CA, United States of America
- Department of Biology, Swarthmore College, Swarthmore, PA, United States of America
| | - Rui Wang
- Department of Biology, Swarthmore College, Swarthmore, PA, United States of America
- Department of Bioengineering, University of California San Diego, La Jolla, CA, United States of America
| | - Sara Martin
- Department of Biology, Swarthmore College, Swarthmore, PA, United States of America
| | - Elizabeth Lanphear
- Department of Biology, Swarthmore College, Swarthmore, PA, United States of America
| | - Eva-Maria S. Collins
- Department of Physics, University of California San Diego, La Jolla, CA, United States of America
- Department of Biology, Swarthmore College, Swarthmore, PA, United States of America
- * E-mail:
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15
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Steele RE, Updegrove MD, Kirolos SA, Mowery L, Martínez DE, Bryant PJ. Reproductive Bet-Hedging and Existence in Vernal Pools as Components of Hydra Life History. THE BIOLOGICAL BULLETIN 2019; 237:111-118. [PMID: 31714853 DOI: 10.1086/705161] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Despite the fact that Hydra has been studied for more than 200 years, we know surprisingly little about its life history. We show that Hydra vulgaris embryos hatch sporadically over a period ranging from a few days to nine months. We also report, for what seems to be the first time, the presence of Hydra in a vernal pool. Phylogenetic analysis and sexual crossing show that this Hydra is a member of the cosmopolitan Vulgaris clade and is not reproductively isolated from other members of the clade. Our findings lead us to hypothesize that Hydra evolved in an unstable freshwater habitat in which survival required that its life cycle include the use of a bet-hedging reproductive strategy and the formation of an embryo that is desiccation resistant and that can remain dormant for long periods of time.
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16
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Siebert S, Farrell JA, Cazet JF, Abeykoon Y, Primack AS, Schnitzler CE, Juliano CE. Stem cell differentiation trajectories in Hydra resolved at single-cell resolution. Science 2019; 365:eaav9314. [PMID: 31346039 PMCID: PMC7104783 DOI: 10.1126/science.aav9314] [Citation(s) in RCA: 177] [Impact Index Per Article: 35.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Accepted: 06/11/2019] [Indexed: 12/31/2022]
Abstract
The adult Hydra polyp continually renews all of its cells using three separate stem cell populations, but the genetic pathways enabling this homeostatic tissue maintenance are not well understood. We sequenced 24,985 Hydra single-cell transcriptomes and identified the molecular signatures of a broad spectrum of cell states, from stem cells to terminally differentiated cells. We constructed differentiation trajectories for each cell lineage and identified gene modules and putative regulators expressed along these trajectories, thus creating a comprehensive molecular map of all developmental lineages in the adult animal. In addition, we built a gene expression map of the Hydra nervous system. Our work constitutes a resource for addressing questions regarding the evolution of metazoan developmental processes and nervous system function.
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Affiliation(s)
- Stefan Siebert
- Department of Molecular and Cellular Biology, University of California, Davis, CA, USA.
| | - Jeffrey A Farrell
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA, USA
| | - Jack F Cazet
- Department of Molecular and Cellular Biology, University of California, Davis, CA, USA
| | - Yashodara Abeykoon
- Department of Molecular and Cellular Biology, University of California, Davis, CA, USA
| | - Abby S Primack
- Department of Molecular and Cellular Biology, University of California, Davis, CA, USA
| | - Christine E Schnitzler
- Whitney Laboratory for Marine Bioscience and Department of Biology, University of Florida, St. Augustine, FL, USA
| | - Celina E Juliano
- Department of Molecular and Cellular Biology, University of California, Davis, CA, USA.
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17
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Transgenesis in Hydra to characterize gene function and visualize cell behavior. Nat Protoc 2019; 14:2069-2090. [DOI: 10.1038/s41596-019-0173-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Accepted: 04/04/2019] [Indexed: 12/13/2022]
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